As large capacity recording media, non-volatile semiconductor memory devices including a NAND-type flash memory are used in various electronic apparatuses. This type of non-volatile semiconductor memory device converts data read from a selected memory cell into a desired voltage level by through a sense amplifier. A read operation of the sense amplifier is called a sense.
As one of sense methods, an all bit line (ABL) method is known. In the ABL method, after a bit line is precharged, the read operation is executed on all bit lines. Then, read data from the memory cell is detected on the basis of an amount of current flowing from the bit line.
In the ABL method, the bit line is first precharged. Then, a transistor connected to a sense node is turned on and a current from the corresponding bit line is transferred to the sense node. However, predetermined setup time is necessary until a gate voltage of the transistor reaches a voltage level to turn on the transistor. The setup time changes for each bit line. As a result, time when the transistor is turned on may also change for each bit line. For this reason, a read characteristic of the sense amplifier is deteriorated.